Conventionally, there has been provided a luminaire, which has a function of transmitting an optical signal, using a visible light as a medium. In other words, a light source for illumination is used also for transmission of the optical signal. In many cases, luminaires transmit different information as optical signals (e.g., information on a location of a luminaire itself as a transmission source).
As this type of luminaire, there has been also provided a luminaire, which is configured to randomly set a timing of transmitting an optical signal (e.g., JP 2006-203669 A).
Here, there is a case where luminaires of transmitting different optical signals are disposed closely to each other. In this case, when a receiver is at a location capable of receiving the optical signals transmitted from the luminaires, collision of the optical signals may occur.
In the case of randomly setting the timing of transmitting the optical signal as described above, if a time period (interval) during which no optical signal is transmitted is too short, the above-mentioned collision of the optical signals may occur with higher probability.